ah, that changes the group by then too
and makes the order by tricky since the the dates will be strings

Select count(*) as count, to_char(publication_date,'dd-MON-yyyy') publication_date from bib_holdings group by to_char(publication_date,'dd-MON-yyyy')
order by to_char(publication_date,'dd-MON-yyyy') -- this probably the wrong order by

alternately use trunc to count by day

Select count(*) as count, trunc(publication_date) publication_date
from bib_holdings
group by trunc(publication_date)
order by trunc(publication_date)